Method of oxidizing tin

ABSTRACT

A METHOD OF PLATING METALLIC ARTICLES WITH TIN AND OF TREATING THE TIN PLATED ARTICLES TO PRODUCE OXIDATION OR THE APPEARANCE OF OXIDATION. THE METHOD INCLUDES AN ACID TREATMENT OF METALLIC ARTICLES WHICH HAVE PLATED WITH TIN BY ANY SUITABLE METHOD OF PLATING, BY MEANS OF WHICH THE TIN PLATE IS ALTERED TO PROVIDE AN APPEARANCE OF OXIDATION AND THEY MAY BE MECHANICALLY TREATED THEREAFTER TO REMOVE SOME OF THE MATERIAL TO PRODUCE AN EFFECT SOMETIMES CALLED &#34;ANTIQUING.&#34;

United States Patent 3,577,282 METHOD OF OXIDIZING TIN Walter A. Schubert, South Elgin, Ill., assignor to Elgiu Metal Casket Company, Elgin, Ill. No Drawing. Filed Apr. 1, 1969, Ser. No. 812,331 Int. Cl. C23f 5/02, 7/00 US. Cl. 1486.24 9 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION In the past, it has been common to plate metal hardware articles such as handles, knobs and levers with silver, which is a metal readily oxidizable. The silver plated parts, when oxidized, have in frequent usage been further treated by polishing or bufiing or by abrasion generally to remove some of the oxidized silver plate and thereby to produce a desired effect in which light and dark areas are provided as desired.

Thus in the past, silver plated articles have been fully oxidized through the silver plated areas and thereafter some of the oxidation has been removed selectively to reveal the original silver plate.

DISCLOSURE OF THE INVENTION An object of this invention is to produce a method of treating metallic articles to give the appearance of oxidation by the use of tin and to avoid the necessity of using an expensive metal such as silver.

Another object is to use tin as a plating metal and to give to it subsequent treatment, after plating, which will produce the appearance of oxidation and this appearance is produced on tin by the method disclosed herein.

Another object of the invention is to treat the tin plated article after it has been given the appearance of oxidation by a further treatment which removes a selected quantity of the coating upon the tin plate and this exposes some of the tin directly. Where the coating is not removed, the appearance of oxidation remains and thus an effect generally known as antiquing is produced.

Thus by the treatment disclosed herein, it is possible to use tin as a plating material instead of using much more expensive silver and by the use of tin as treated according to the method described herein, the appearance of the final article is in all essential respects the same as a silver plated article.

Other objects will become apparent from a reading of the specification and claims.

The method of the present invention comprises the following steps:

(1) A metallic article, which may be of any metal which can accept tin as a plating material, is plated with tin by any conventional method. The invention does not reside in the type of tin plating or method of accomplishing it. If desired, the article may be plated with copper or nickel or both prior to the tin plating. Where this is done, the subsequent tin plating is generally smoother than is the case Where the tin is plated directly upon the base metal. The initial plating of copper or nickel or both is a Patented May 4, 1971 matter of choice and it is not necessary and the subsequent steps outlined below may be carried out equally well Whether or not the tin plate is deposited directly upon the base metal or upon a coating of copper or nickel.

(2) After the article has been plated with tin, it is rinsed in water. The temperature of the water is not critical. Generally, the rinse may be in cool water.

(3) After the plating and rinsing, the article is placed in a solution of water and 5% sulphuric acid by volume and A oz. per gallon of water copper sulphate. The tin plated article is left in this bath until the desired color is produced. As the article remains in the acid bath, the visible surfaces take on the appearance of oxidation very similar to, if not identical with, the appearance which a silver plate takes on at the time that it is Oxidized.

(4) When the desired color or density of color has been achieved, the article is removed from the sulphuric acid bath and is rinsed in cold water.

(5) Thereafter, it is rinsed in hot water.

(6) The part is now dried. No special type of drying is required and the article may merely be permitted to dry at room temperature.

(7) After the part has been dried, some of the color is relieved or removed by means of a wire brush, which may be a rotary brushing wheel. If desired, pumice or other abrasive material may be used during the brushing operation, with the result that some of the coating material which has the appearance of oxidation is removed. It is a matter of choice how much of the coating material is removed and thus how much of the tin plating is exposed. Generally, enough of the coating is removed to create the appearance known as antiquing. Customarily, the coating will be permitted to remain on the contours and details of the article which constitute elevations and depressions with respect to the major part of the area of the article.

(8) After the coating has been removed or relieved to the desired extent, the article may be laquered. The effect of this is to provide a protective coating which tends to protect the article from damage due to abrasion in handling subsequent to manufacture. This step is not essential and does not involve or cause a change in appearance or color of the article.

It is immaterial whether or not the method described actually produces true chemical oxidation of the tin plate. It produces an appearance substantially identical with that of oxidized silver plate. Some oxidation may take plate or the color which is produced in the acid bath may comprise a copper sulphate coating overlying the tin plated article and the appearance of the article is essentially identical with the appearance of an oxidized silver plated article.

I claim:

1. The method of treating a metallic article which comprises the following steps plating the article with tin,

rinsing said article in water,

subjecting it to a bath comprising water, 5% sulphuric acid by volume and oz. of copper sulphate per gallon of water,

thereafter, rinsing said article in water,

drying said article, and

removing some of the coating material from said article and uncovering some of the tin plate.

2. The method of claim 1 characterized by the fact that the second rinsing is done first in cold water and subsequently in hot water.

3. The method of claim 1 further characterized by the fact that the portion of coating which is removed by abrasion.

4. The method of claim 3 characterized by the further step of applying transparent lacquer to the article after 9. The method of claim 8 characterized by the removal the removal of some of the coating. of some of the coating by abrasion and by the applica- 5. The method of claim 1 characterized by the further tion of transparent lacquer to the article.

step of applying transparent lacquer to the article after the removal of some of the coating. References Cited 6. The method Of claim 1 characterized the further 5 and Bonney Chemical Coloring of Metals van step of plating the article with copper prior to the tin Nostrand and 192 pp 1 3, 224, 225. plating.

7. The method of claim 1 characterized by the further RALPH S. KENDALL, Primary Examiner step of plating the article with nickel prior to the tin 10 plating. U.S. Cl. X.R.

8. The method of claim 1 characterized by the further 0 -3 step of plating the article with copper and tin prior to the tin plating. 

